Homogeneous carbon monoxide hydrogenation on multiple sites: a dissociative pathway to oxygenates

Abstract

7417found in Table I for several solvents and for different synthetic material prepared independently by two different workers. Free ligand 1,lO-phenanthroline impurity emission is ruled out by the data in Figure 1; adding AgCFsSO3 in small amounts does not alter the emission properties; the complexes are "pure" by elemental analysis and 'H NMR and by IR immediately prior to and after emission spectroscopy measurements. None of the solvents or reagents used in synthesis, workup, or purification exhibits emission like that (lifetime, energy) found for the four cations for L = 1,lO-phenanthroline. All sources of "impurity" emission are thus ruled out; the essential results detailed in Table I and Figure 1 are also independent of concentration in the range 10-4-10-5 M.

Synthesis of the Highly Reduced [Fe6C(CO)15]4– Carbonyl Carbide Cluster and Its Reactions with H+ and [Au(PPh3)]+

“…In all cases, after less than 1 h, the dihydride 4 decomposes, yielding 1 as the major product in solution (by IR spectroscopy). A similar behavior was observed whilst investigating the protonation of [HFe 4 (CO) 12 ] 3-, which eventually resulted in [Fe 4 (CO) 13 ] 2and [HFe 4 (CO) 13 ]via an [H 2 Fe 4 (CO) 12 ] 2intermediate. [34] The reaction of 2 with a slight excess of Au(PPh 3 )Cl afforded the aurated dianion [Fe 6 C(CO) 15 (AuPPh 3 ) 2 ] 2- (5) [Equation (4)], which was isolated and structurally characterized as its [Et 4 N] 2 [Fe 6 C(CO) 15…”

“…Iron carbide clusters have been thoroughly investigated and represented milestones for the understanding of the reactivity and activation of CO and carbides on metal surfaces and nanoclusters, leading to major contributions to the development of the cluster-surface analogy. [9][10][11][12][13][14][15][16] Moreover, they have been widely employed for the preparation of miscellaneous dimetallic carbonyl carbide clusters. [17][18][19][20][21][22][23][24][25][26][27] The oxidation of the [Fe 6 C(CO) 16 ] 2-(1) cluster anion results in the partial removal of Fe atoms, leaving the carbide exposed to further reactions.…”

“…Both 3 and 4 are not stable enough to be isolated and rapidly decompose, yielding the parent dianion 1. The reaction of 2 with a slight excess of Au(PPh 3 )Cl affords the aurated dianion [Fe 6 C(CO) 15 (AuPPh 3 ) 2 ] 2- (5), which has been isolated and structurally characterized as its [Et 4 N] 2 [Fe 6 C(CO) 15 CO ligands of 1, leading, for instance, to [Fe 6 C(CO) 13 (NO) 2 ] 2-, [29] [Fe 6 C(CO) 15 (NO)] -, [Fe 6 C(CO) 11 (NO) 4 ], [30] and [Fe 6 C(CO) 15 -(SO 2 )] 2-. [31] Moreover, the addition of an [Au(PPh 3 )] + fragment to 1 affords the heptanuclear cluster [Fe 6 C(CO) 16 (AuPPh 3 )] -.…”

“…Thereafter, other carbonyliron carbide clusters were discovered, and they may be grouped into three main categories: (1) tetrairon clusters with a butterfly structure and a semi‐exposed carbide, such as [Fe 4 C(CO) 13 ], [Fe 4 C(CO) 12 ] 2– , [HFe 4 C(CO) 12 ] – ,, [HFe 4 CH(CO) 12 ]; (2) pentairon clusters with a square‐pyramidal structure and a basal semi‐exposed carbide, for example, [Fe 5 C(CO) 15 ], [Fe 5 C(CO) 14 ] 2– ; (3) the hexairon octahedral [Fe 6 C(CO) 16 ] 2– cluster featuring a fully interstitial carbide atom. Iron carbide clusters have been thoroughly investigated and represented milestones for the understanding of the reactivity and activation of CO and carbides on metal surfaces and nanoclusters, leading to major contributions to the development of the cluster‐surface analogy Moreover, they have been widely employed for the preparation of miscellaneous dimetallic carbonyl carbide clusters …”

Carbidocarbonyl clusters of iron

“…Iron is so far unique in that it alone forms carbidocarbonyl clusters containing only four metal atoms, and the discovery of this class of compounds and of the reactivity of its members has provided one of the more intriguing developments in cluster chemistry over the last few years. We reported in 1979 that the cluster-bound carbon atom, which was apparently inert in Fe5C and Fe6C clusters, could display novel chemistry if exposed by the removal of some of its surrounding metal atoms, reducing the coordination number of the carbon atom to four in an open, butterfly geometry (Bradley et al 1979). This, the first observation of the reactivity of a cluster-bound carbon atom, resulted from the partial fragmentation of the octahedral carbide cluster [Fe6C(CO)16]2~, 2.…”